ZFS on Ubuntu16 (booting from non-zfs volume) does not mount /var from ZFS-Dataset

[typoworx-de]

I'm trying to migrate my disk to ZFS whereas I'm using an SSD-Drive (LVM for RootFS) and a Hard-Disk as Storage for my other Data setup with ZFS.

My RootFS relies on LVM-Volume (works). I want to have '/var' and some sub-folder (like /var/www) on ZFS.

I already tried this to fixup this issue:

1. Adding the rpool/dataset for var to /etc/init/zfs 'ZFS_INITRD_ADDITIONAL_DATASETS'

2. zfs set mountpoint=legacy rpool/var

3. adding rpool/var to fstab:

4. tried the workaround mentioned in Mounts datasets too late in boot process #101

5. tried to trigger '/usr/bin/zpool import -a' with own script in '/etc/initramfs-tools/scripts/init-top/' and '/etc/initramfs-tools/scripts/init-premount/' (my 'echo' inside the script not even got shown during boot ...)

So far I'm just able to boot into recovery. Manually doing 'zpool import -a' and 'mount -a' works! But on boot it stuck on local-premount and systemd begins to complain about missing mount for '/var'!

How can this be fixed or is this only working using zfs as root also?! As mentioned currently I'm afraid of moving RootFS to ZFS as there are already so much problems just trying to make '/var' mount from ZFS rPool in place at boot already!

[c0dyhi11]

@typoworx-de I have this same issue.
Did you ever find a solution?